Morphology of 3,4,5,3',4'-pentachlorinated biphenyl-induced change in canine lung

We investigated the light and electron microscopical changes of the lung in dogs treated with 3,4,5,3',4'-pentachlorinated biphenyl (PenCB). Beagle dogs were orally administered with 0.1 mg/kg of PenCB, and sacrificed 3, 5 and 7 weeks after the PenCB administration. Light microscopically, bronchiolar epithelial cells showed cytoplasmic vacuolization, which was most prominent 5 weeks after the PenCB administration. Electron microscopically, nonciliated bronchiolar epithelial cells (Clara cells) revealed degradation of glycogen particles, swollen, irregularly arranged smooth endoplasmic reticulum, and swollen mitochondria, while no significant change was found in other epithelial cells. The endothelial cells also showed no significant change except for increased number of cytoplasmic vesicles. This is a first report on halogenated hydrocarbon-induced degradation of glycogen particles in Clara cells.     

Structural basis for the spotted appearance of amphibian neuromuscular junctions stained for synaptic vesicles

We have compared the distribution of vesicles in amphibian motor nerve terminals determined by electron microscopy and by functional labeling with the styryl dye, FM2-10. Our aim was to resolve apparent discrepancies in the literature on the distribution of vesicles determined by the two procedures. Electron photomicrographs of non-serial cross sections of terminal branches were analyzed by stereological procedures to obtain indices of the terminal and vesicle areas. Terminal cross sectional area varied 3-fold on average along terminal branches and was largest particularly when active zone was present in the section. The vesicle area index (a measure of vesicle abundance) was highly correlated with the terminal area index, suggesting that the average density of vesicles is constant throughout the branches. When the data were separated according to whether active zone was present or not in a section, we found a small (26%) but significant increase in the average density of vesicles in active zone compared with non-active zone regions in the terminal. The distribution of spots along terminal branches following vesicle staining with FM2-10, as well as with antibodies to vesicle proteins, suggested that vesicles were distributed in highly concentrated clusters. However, the degree of variation between spot and inter-spot staining intensities found with the FM-dye was similar in magnitude to that for terminal cross sectional area determined from the electron microscopy. We conclude that the spotty pattern of stained vesicles seen with the optical microscope results primarily from vesicle accumulations associated with terminal varicosities.     

Formation of synaptic vesicles in the superior cervical ganglion of cat: choline dependency

Summary De novo formation of synaptic vesicles was studied electron microscopically in synapses of the superior cervical ganglion of cat. Following prolonged electrical stimulation in a choline deficient condition, almost complete loss of vesicle content was observed. After choline administration, together with the partial restoration of transmission, the reappearance of vesicles could be seen in nerve terminals. In interpreting our observations, the double role of choline (transmitter precursor and membrane constituent) is emphasized.     

Lysosomal integral membrane proteins exhibit region and cell type specific distribution in the epididymis of the adult rat

The epididymis, a post-testicular site required for maturation and storage of spermatozoa, is actively involved in exocytic and endocytic events, two phenomena likely to depend on the integrity of the lysosomal system. To study the lysosmal system of the epididymis, five monoclonal antibodies, previously characterized as recognizing five distinct lysosomal integral membrane proteins (LIMPs 1–5), were used as molecular probes of lysosome distribution in cells lining the epithelium. Immunocytochemical localization of LIMPs, using biotin-streptavidin immunoperoxidase methodology, was performed on frozen sections of adult rat epididymides and in cell cultures prepared from either the caput or cauda epididymis. In frozen sections, a heterogeneous distribution of the different LIMPs along the length of the epididymis was observed. For example, the distribution of LIMP 1 (35–50 K) was detected in all cells of the caput and quite dramatically in clear cells of the distal caput, corpus, and cauda epididymis, but specifically not in the principal cells of the distal caput, corpus, and cauda. In contrast, LIMP 2 (64–71 K) was present in all cells of the epidiyms, except clear cells. LIMPs 4 and 5 (93 K and 93 K) were detected in all epididymal cells, including the clear cells. Finally, whereas the regional and cell type distribution of LIMP 3 (74 K) in the epididymis was identical to that of LIMPs 4 and 5, the nature of the vesicles immunostained was distinct. In cultured cells, the general immunostaining patterns observed in vivo were maintained during the duration of the primary cultures for all five LIMPs. Our results begin to address the molecular heterogeneity of the lysosomal system along the lenght of the epidiymis, and may suggest in part a basis for underlying structural and functional characteristics of the epididymis leading to the sequential maturation of sperm.     

Formation of secretion granules in the Golgi apparatus of pancreatic acinar cells of the rat

The three-dimensional structure of the Golgi apparatus and its components has been analyzed in sections of pancreatic acinar cells by using stereopairs of electron microscope photographs. Pancreatic tissue fixed in glutaraldehyde was postfixed in reduced osmium, and the sections were stained with lead citrate. Tissues were also treated to demonstrate phosphatase activity (i.e., nicotinamide adenine dinucleotide phosphatase, NADPase; thiarnine pyrophosphatase, TPPase; cytidine monophosphatase, CMPase). The following stacked components were observed along the branching, anastomotic, continuous, ribbon like Golgi apparatus. (1) On the cis-face of the Golgi stack there was a tubular membranous network known to be osmiophilic and referred to as the cis-osmiophilic tubular network or cis-element. (2) A first, poorly fenes-trated saccule, unreactive for the phosphatases tested, was slightly distended in places and contained a fluffy granulofilamentous material. (3) The subjacent three or four saccules, reactive for NADPase and/or TPPase, showed dilated portions containing a granulofilamentous secretory material similar to that filling the rest of the saccule. They also showed nondilated portions perforated with large fenestrations, some of which were in register and formed wells containing 80-nm vesicles. The dilated portions of these saccules were present at random along the length of the saccules and were not located exclusively at their edges. (4) The remaining one or two elements of the stack, CMPase positive, showed dilated spheroidal portions or prosecretory granules containing a homogeneous secretory material and flattened fenestrated regions free of secretory material and having the appearance of networks of narrow membranous tubules. (5) Lastly on the trans-aspect of the stack there were detached prosecretory granules reactive for CMPase and surrounded by a corona of small vesicles, and smooth-surfaced spherical CMPase-negative granules having a denser content that were identified as fully formed secretion granules; there were also occasional free trans-tubular networks strongly reactive for CMPase that appeared to undergo fragmentation and numerous small vesicles free from acid-phosphatase activity. These various images were interpreted as indicating that prosecretory granules formed in relation to two or three fenestrated saccules on the trans-side of the stack. Such granules, following their detachment from the trans-face of the stack, their separation from trans-tubular networks, and condensation of their content, yielded mature secretion granules.     

Lysosomal integral membrane proteins exhibit region and cell type specific distribution in the epididymis of the adult rat.

The epididymis, a post-testicular site required for maturation and storage of spermatozoa, is actively involved in exocytic and endocytic events, two phenomena likely to depend on the integrity of the lysosomal system. To study the lysosomal system of the epididymis, five monoclonal antibodies, previously characterized as recognizing five distinct lysosomal integral membrane proteins (LIMPs 1-5), were used as molecular probes of lysosome distribution in cells lining the epithelium. Immunocytochemical localization of LIMPs, using biotin-streptavidin immunoperoxidase methodology, was performed on frozen sections of adult rat epididymides and in cell cultures prepared from either the caput or cauda epididymis. In frozen sections, a heterogeneous distribution of the different LIMPs along the length of the epididymis was observed. For example, the distribution of LIMP 1 (35-50 K) was detected in all cells of the caput and quite dramatically in clear cells of the distal caput, corpus, and cauda epididymis, but specifically not in the principal cells of the distal caput, corpus, and cauda. In contrast, LIMP 2 (64-71 K) was present in all cells of the epididymis, except clear cells. LIMPs 4 and 5 (93 K and 93 K) were detected in all epididymal cells, including the clear cells. Finally, whereas the regional and cell type distribution of LIMP 3 (74 K) in the epididymis was identical to that of LIMPs 4 and 5, the nature of the vesicles immunostained was distinct. In cultured cells, the general immunostaining patterns observed in vivo were maintained during the duration of the primary cultures for all five LIMPs. Our results begin to address the molecular heterogeneity of the lysosomal system along the length of the epididymis, and may suggest in part a basis for underlying structural and functional characteristics of the epididymis leading to the sequential maturation of sperm.     

Ultrastructural study of endocytosis of Chlamydia trachomatis by McCoy cells.

The entry of Chlamydia trachomatis into McCoy cells (fibroblasts) was studied by transmission electron microscopy. On adsorption of elementary bodies (EBs) to host cells at 37 degrees C, the EBs were bound primarily to preexisting cell-surface microvilli. They were also observed in coated pits located at the bases of the microvilli and along smooth surfaces of the host cells and were internalized within coated vesicles at this temperature. Postembedding immunogold labeling on Lowicryl thin sections with anti-clathrin antibody as the primary reagent revealed the gold marker localized in pits and vesicles containing chlamydiae. Some EBs were present in smooth-surfaced invaginations at or near the bases of microvilli and in vesicles devoid of distinguishable coat material. A similar entry process was observed with centrifugation-assisted inoculation of EBs onto the McCoy cells. Individual EBs were initially internalized into tightly bound endocytic vesicles. However, within 1 to 3 h postinfection, multiple C. trachomatis EBs were observed in large, loosely bound vesicles. Evidence suggests that vesicles containing C. trachomatis may have fused with one another early in the infectious process. These results indicate that chlamydiae can exploit the specific process of adsorptive endocytosis for entry into host cells and for translocation to a given intracellular destination, which may be different for each species.     

Location of large core synaptic vesicles in the dorsal gray matter of the cat and dog spinal cord

Cross sections of aldehyde-perfused, Epon-embedded cat and dog spinal cord examined with an electron microscope display numerous synaptic vesicles with electron-opaque cores along the medial and lateral margins of the dorsal gray matter (laminae I, II, III). The cored vesicles, 750 – 1500 A in diameter are located in synaptic sacs and in small unmyelinated axons. They occur in small numbers throughout the apical gray matter but are much more numerous in a narrow band immediately adjacent to the white matter. Their numbers and location should be of value in studies on the nature and origin of this type of synaptic vesicle.     

Periterminal synaptic organization of primary afferents in laminae I and IIo of the rat spinal cord, as shown after anterograde HRP labelling

Summary The fine structure and periterminal synaptology of the primary afferent terminations in laminae I and IIo are examined in the rat, following anterograde labelling with horseradish peroxidase applied to the right C₅-dorsal root. Labelled varicosities observed along the terminal arbors in parasagittal thick sections were relocated in ultrathin sections by electron microscopy. The labelled terminal profiles generated by the three primary afferent plexuses which can be identified by light microscopy in laminae I-IIo had similar fine structural features, except that axo-axonal contacts, although rare, were more frequent in the medial network plexus. Primary boutons were packed with agranular spherical vesicles and some large granular vesicles, and were mostly presynaptic to profiles of dendritic trunks of marginal cells. Unlabelled axonal profiles, either light with some flattened vesicles, or dense with round vesicles, were also presynaptic at symmetrical or asymmetrical contacts, respectively, to those dendritic profiles. It is suggested that such knobs of intrinsic origin are responsible for postsynaptic modulation of the primary noxious input. Although the 20 m wide lamina IIo belongs cytoarchitectonically to lamina II and can be distinguished from lamina I by a decreased amount of myelinated fibres and large dendritic profiles, the periterminal synaptology was here found to be the same as in lamina I.     

Cortical and tectal afferent terminals in the suprageniculate nucleus of the cat

The suprageniculate nucleus (Sg) of the cat was observed electron microscopically after wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injection into the anterior ectosylvian visual cortical area (AEV) and superior colliculus (SC). Small axon terminals filled with round synaptic (RS) vesicles were labeled with HRP injected into the AEV and SC, whereas large axon terminals containing round synaptic (RL) vesicles were labeled after HRP injection in the SC. After producing a lesion in the AEV and adjoining orbito-insular cortex and injecting WGA-HRP into the SC, degenerated terminals and HRP-labeled RS terminals were occasionally found to make synaptic contacts with a single dendritic profile of Sg neurons.     

Use of tannic acid to study cytoplasmic vesicles and membrane invaginations in epididymal fat pads of ageing mice

A staining technique based upon the known ability of tannic acid to selectively stain the outer layer of the triple-layered plasma membrane was used, along with electron microscopic examination of stained, serial sections, to differentiate between surface invaginations, clusters of invaginations, free vesicles and tubular channels in epididymal fat pads from young, fed and fasted mice and from old, fed mice. A preliminary semiquantitative evaluation of the average number of each type of structure per cell was attempted. There were no significant numbers of free cytoplasmic vesicles of approximately 50 nm diameter (the dimension of most surface invaginations) under any conditions studied. Most apparent vesicles were stained by tannic acid and were, therefore, actually invaginations of the plasma membrane. There were no tubular channels of this size seen in any of the electron micrographs examined in serial sections. We estimated that there are about 50 single invaginations per micron2 of plasma membrane surface in both young and old fed mice. In addition there were about 20 invaginations/micron2 grouped as clusters of 2-15 per group (mean, 4 per group) in the fed mice. There was a tendency for the number of invaginations in clusters to increase during fasting; about 40% of the surface invaginations were grouped in clusters in adipocytes of fasted mice. Although there was no effect of ageing on the concentrations of surface invaginations or in their groupings as clusters, the total number of invaginations per cell must have increased almost 3-fold as the cells enlarged. The function of these surface invaginations and deeply penetrating groups of invaginations remains to be elucidated.     

Ultrastructure of the primate carotid body: a morphometric study of the glomus cells and nerve endings in the monkey (Macaca fascicularis)

Summary The carotid body of the monkey (Macaca fascicularis) was studied at both the light and electron microscopic levels in an effort to provide a detailed quantitative characterization of this chemoreceptor organ in the primate. Structurally, the monkey carotid body was organized into lobules of from three to eight glomus cells (in section) and their ensheathing supporting cells. Interspersed among the lobules was abundant connective tissue stroma, fibroblasts and mast cells. Fenestrated capillaries, small arterioles and venules also permeated the organ. Each supporting cell partially ensheathed about three glomus cells and could be easily differentiated from glomus cells by their darker cytoplasmic staining, lack of dense-core vesicles and angular nuclear profile. Glomus cells exhibited an intense catecholamine histofluorescence and contained abundant dense-core vesicles. On the basis of dense-core vesicle size, shape and numerical density, four types of glomus cells were identified. The most common type (62% of all glomus cells) contained vesicles with an average diameter of 219 nm and a density of 8 vesicles per m² of cytoplasm. The second type possessed larger vesicles (264 nm in diameter) and accounted for about 14% of all glomus cells. A third type of glomus cell contained smaller (167 nm) and fewer (5 vesicles per m²) dense-core vesicles. The fourth type of glomus cell contained pleomorphic-shaped vesicles with a maximal diameter of 232 nm. Each of these last two types accounted for about 12% of all glomus cells. All four types of glomus cells were innervated, averaging 1.43 nerve endings per glomus cell (in sections). Nerve endings were primarily of the bouton-like variety averaging 2 m² in sectional area and containing 34.3 clear-core synaptic vesicles (average size 73.5 nm in diameter) per m² of cytoplasm. Of the 57 nerve endings examined in single sections, 16% displayed junctions typical of synaptic specializations and most of these were presynaptic to glomus cells. Glomus cell-glomus cell synapses were not observed. Based on these quantitative observations and on previous studies of carotid body cytoarchitecture in other laboratory species, it appears that the primate organ most closely resembles the cat carotid body, although several differences exist.     

Lateral canthal support system in Japanese

The present study aimed to elucidate microscopically the precise structure of the generally termed 'lateral canthal tendon' (LCT). Specimens from 9 post-mortem lower eyelids of 6 Japanese aged from 72 to 91 years old at death were fixed in 10% buffered formalin, and microscopically examined. Specimens were excised as exenterated samples including an area 5 mm wider than the orbital aperture. The removed contents were further incised longitudinally on the central eyelid and also incised parallel to the upper eyelid margin on the site 3 mm from its margin. After the preparation of microscopical examination, sections of all 9 eyelids were stained with Hematoxylin and Eosin. We found that the structure generally termed LCT consisted of two definitive different layers microscopically. The superficial layer was only an orbital septum (septal band). It was mainly constituted of thick fibers between adipose-rich tissues. The deep layer continued from the tarsus and projected posteriorly; which was a ligament (tarsoligamentous band). This tissue was constituted by thin, minute fibers with little adipose tissues. The structure generally termed LCT is not a tendon but a complex constitution of an orbital septum and a ligament; which we named, in a mass, 'lateral canthal bands', cooperatively supporting the lateral canthus.     

A core-conductor model of the cardiac Purkinje fibre based on structural analysis

1. Structural analysis of voltage clamp preparations of sheep cardiac Purkinje fibres was carried out using methods based on light and electron microscopic observations. Results demonstrate the marked structural variability in preparations that appear, outwardly, simple.2. The length of the cell aggregate was measured in vitro, and the mean area of cross-section, by light microscopic methods in serially sampled transverse sections. The number of intercellular clefts and path lengths of cell profiles distributed at the lateral surface and along clefts were determined from photomicrographs. Accuracy of these estimates was improved by obtaining, electron microscopically, values representing the degree of membrane folding in longitudinal and transverse planes.3. Cleft width was evaluated from electron micrographs. Measurements made on sections that there tilted through wide arcs with a goniometer indicate that cleft width is quite variable and, on average, somewhat greater than 400 A.4. A three-dimensional core-conductor model is presented to aid in quantitative interpretation of electrophysiological experiments. Application of the model to individual preparations requires evaluation of the length and perimeter of cross-section of cell aggregates and of the mean number, width and depth of intercellular clefts, with appropriate corrections for fine sarcolemmal folding. Methods are given for estimating these structural parameter values from measurements of external dimensions of cell aggregates.5. The core-conductor model is applied in an accompanying analysis of the linear electrical characteristics of Purkinje membrane.     

Tridimensional structure of the Golgi apparatus in type A ganglion cells of the rat

The three-dimensional structure of the whole Golgi apparatus and of its components in type A ganglion cells was examined in thin and thick sections by low- and high-voltage electron microscopy. At low magnification, in 10-μm-thick sections of osmicated cells, the Golgi apparatus formed a broad, continuous perinuclear network. At higher magnification and in thinner sections of cells impregnated with uranyl acetate-lead-copper citrate or postfixed in K-ferrocyanide-reduced osmium, the Golgi apparatus appeared as a heterogeneous structure in which saccular regions characterized by stacks of saccules alternated with intersaccular regions made up of branching membranous tubules which bridged the saccules of adjacent stacks. The saccular regions consisted of the following superimposed elements: (1) a cis-osmiophilic element made up of anastomosing tubules; (2) two or three saccules negative for the phosphatases tested (i.e., nicotinamide adenine dinucleotide phosphatase = NADPase, thiamine pyrophosphatase = TPPase, and cytidine monophosphatase = CMPase); (3) two saccules showing TPPase activity; and (4) one to three trans-sacculotubular elements showing a “peeling-off” configuration, one of which showed CMPase activity. The saccules (phosphatase-negative) on the cis-side of the Golgi stacks showed, in addition to small circular pores, larger perforations in register. The cavities thus formed in the stacks of saccules, called “wells,” always associated with small 80-nm vesicles, had a pan shape with the mouth directed toward the cis-face and the bottom closed by a TPPase-positive saccule. In face views of the saccules, the smallest of these perforations showed either a crescent shape, due to the presence of a bud on one side of the perforation, or a circular shape with a single small 80-nm vesicle in the center which was occasionally attached to the saccule by a filiform stalk. Such smaller cavities were considered as the precursors of the larger perforations and eventually of the wells. The small 80-nm vesicles seen in the small cavities or in the wells appeared to form in situ and possibly migrate toward the cisternae of endoplasmic reticulum seen proximal to the cis-face of the stack of saccules. Small 80-nm vesicles were also numerous in the intersaccular regions, along the lateral- and trans-aspects of the Golgi stacks, while larger, 150-to 300-nm vesicles, coated and uncoated, were seen only on the trans-face of the Golgi stacks in proximity to the trans-sacculotubular elements which appear to “peel off” from the Golgi stacks.     

No raphe identified in the orbicularis oculi muscle

This study was performed to elucidate whether the raphe of the orbicularis oculi muscle (raphe) exists or not. Nine upper eyelids of 6 Oriental cadavers with ages at death ranging from 72 to 91 years were dissected; 6 for gross dissections and 3 for histological slice sections. After removing the lateral half of the eyelid skin, the lateral part of the orbicularis oculi muscle and its subjacent tissue were observed macroscopically. The full layered tissue of the 8 mm lateral part from the orbital rim was incised perpendicularly and sections sliced, which were then observed microscopically after staining with the hematoxylin and eosin. The raphe was not identified macroscopically or microscopically. The lateral part of the orbicularis oculi muscle was continuous without the tendinous intercalation; under it, fibrous connective tissue corresponding to the lateral orbital thickening was observed, and in which the band configuration, microscopically the tendinous structure, was formed. The raphe was not identified. The physiological role of the lateral part of the orbicularis oculi muscle is maintained by a less tight attachment of the lateral orbital thickening, but not by the raphe.     

Development of synaptic structure and function in organotypic cultures of the rat hippocampus

The sequence of development of synapses, as well as the ultrastructure of axonal growth cones, has been investigated electron microscopically in tissue cultures of the newborn rat hippocampus. During differentiation of the tissue cultures, the formation of synapses is preceded by identifiable growth cones. A characteristic feature of axonal growth cones is the presence of numerous large clear vesicles which vary in diameter from ~100 to 150 nm. The first immature synapses were formed on the 5th, 6th or 7th day in vitro on the growth cones of differentiating neuronal processes. Axonal growth cones are occasionally found to be presynaptic to a dendrite. At first axo-dendritic synapses, most of them being en passant, arise, whereas axo-somatic and axo-spinous-dendritic synapses of different complex structures appear later.It is suggested that the earliest signs of synaptogenesis are vesicular structures (‘growth’ vesicles and few synaptic vesicles), which occur in growth cones, axons and presynaptic boutons of immature synaptic contacts even before formation of the specialized pre- and postsynaptic membranes.     

Dopaminergic nerve endings in the neostriatum of the rat—2. Radioautographic study following local micro-injections of tritiated dopamine

Local micro-injections of tritiated dopamine were made into the nucleus caudatus-putarnen of rats in order to identify the dopamine-containing nerve endings by high-resolution radioautography and to correlate with our results obtained with micro-injections of 5-hydroxydopamine. The density of silver grains (number per square unit) over the different kinds of nervous elements and glia was studied in single sections, showing a rather weak accumulation over mitochondria and over numerous synaptic contacts (37%) which were of the asymmetric type. Labeling was subsequently studied using semi-serial ultra-thin sections. Only about 10% of the latter contacts remained labeled in two adjacent sections. Their presynaptic areas usually contained small crowded synaptic vesicles and belonged mainly to the Type III of Bak et al. (1975).This is in agreement with our previous findings which demonstrated that about 10% of the neostriatal synaptic contacts, belonging principally to the same type and concentrating 5-hydroxydopamine, can be considered as containing dopamine.     

Sensitivity of Purkinje cell dendrites to glutamic acid

Summary The distribution of glutamate sensitive sites was studied in vitro in thin cerebellar sections from guinea-pigs, in which Purkinje cell bodies and some of the principal dendrites were identified microscopically. Glutamate administered near the cell body induced firing. Stronger excitation, however, was produced when glutamate was administered to the molecular layer along a strip of tissue extending from the soma of the cell under study towards the pial surface of the slice. Excitation induced by glutamate slowly declined in some cells during prolonged administration. D-Glutamate was a weaker excitant than the L-isomer. These results suggest that the dendrite of the Purkinje cell is more sensitive to glutamate than the cell soma.     

Endocytosis in the epithelium of the mouse oviduct

We studied the pathway of serum protein transport into the lumen of the mouse oviduct by localizing several tracer proteins in the oviduct after intravenous injection on days 1, 5, and 11 of pregnancy. Fluorescent proteins were observed in the lamina propria and in vesicles in the lumenal epithelial cells mainly in the preampulla segment on days 5 and 11 of pregnancy. In the isthmus, there was much less fluorescence in the lamina propria and no fluorescent vesicles in lumenal epithelial cells. This is similar to previous observations on day 1 and indicates that the uptake of serum proteins into lumenal epithelial cells in the preampulla is not limited to the time when embryos are present in the oviductal lumen. Horseradish peroxidase (HRP) was present in the lamina propria of the preampulla on days 1 and 5, but direct tracer movement into the oviductal lumen was blocked by the epithelial junctional complexes. Within the epithelial cells, HRP was localized in endocytic vesicles along the basolateral membrane, multivesicular bodies (mvb), elongated dense bodies below the nucleus (bdb), and many small vesicles near the apical surface of the cells. Ferritin was also used as a tracer and was observed in the same locations as HRP. Acid phosphatase in the epithelial cells of the preampulla on day 1 was localized in mvb and bdb, indicating that these structures are lysosomes. It appeared that HRP and ferritin followed two pathways after basolateral endocytosis by the epithelial cells in the preampulla: (1) they were transported to apical vesicles that may release their contents into the oviductal lumen, or (2) they were transported to lysosomes. These observations suggest the occurrence of an intracellular vesicular transport system in the preampulla for the transfer of serum proteins to the oviductal lumen in mice.